perf(web): share service health snapshots

apps/web/src/lib/server/datasources/dashboard-datasources.test.ts

@@ -3,7 +3,7 @@ import {
   DASHBOARD_SCHEMA_VERSION,
   type DashboardDocument,
 } from "@dimensionlab/dashboard-model";
-import { resolveDashboardDatasources } from ".";
+import { resolveDashboardDatasources, resolveDashboardTile } from ".";
 
 describe("dashboard datasource resolution", () => {
   test("hydrates telemetry, service health, weather, and summary data from live adapters", async () => {
@@ -124,6 +124,100 @@ describe("dashboard datasource resolution", () => {
     expect(resolved).not.toBe(testDocument);
     expect(testDocument.telemetry[0].value.value).toBe(1);
   });
+
+  test("shares service health snapshots across aggregate tile hydration", async () => {
+    let resolveFetch: ((response: Response) => void) | undefined;
+    const fetch = vi.fn((input: RequestInfo | URL) => {
+      const url = String(input);
+      if (url !== "https://service.example/health") {
+        throw new Error(`Unhandled test request: ${url}`);
+      }
+
+      return new Promise<Response>((resolve) => {
+        resolveFetch = resolve;
+      });
+    });
+    const document = testDashboard();
+
+    const moduleTile = resolveDashboardTile(
+      document,
+      { kind: "module", id: "runtime-health-summary" },
+      { fetch },
+    );
+    const statusTile = resolveDashboardTile(
+      document,
+      { kind: "status", stripId: "footer", id: "system-status" },
+      { fetch },
+    );
+
+    await Promise.resolve();
+    expect(fetch).toHaveBeenCalledTimes(1);
+
+    resolveFetch?.(jsonResponse({ status: "UP", ping: 42 }));
+    expect(await moduleTile).toMatchObject({
+      state: "ready",
+      item: {
+        id: "runtime-health-summary",
+        severity: "ok",
+        value: "all systems operational",
+      },
+    });
+    expect(await statusTile).toMatchObject({
+      state: "ready",
+      item: {
+        id: "system-status",
+        severity: "ok",
+        value: "All systems operational",
+      },
+    });
+  });
+
+  test("isolates service health snapshots by datasource fetch context", async () => {
+    const firstFetch = vi.fn(async () =>
+      jsonResponse({
+        status: "UP",
+        ping: 42,
+      })
+    );
+    const secondFetch = vi.fn(async () =>
+      jsonResponse({
+        status: "DOWN",
+        ping: 0,
+      })
+    );
+    const document = testDashboard();
+    document.serviceGroups[0].services[0] = {
+      ...document.serviceGroups[0].services[0],
+      id: "api-isolated",
+      datasource: {
+        type: "external",
+        adapter: "http-status",
+        reference: "GET https://service.example/isolated",
+      },
+    };
+
+    await resolveDashboardTile(
+      document,
+      { kind: "status", stripId: "footer", id: "system-status" },
+      { fetch: firstFetch },
+    );
+    const second = await resolveDashboardTile(
+      document,
+      { kind: "status", stripId: "footer", id: "system-status" },
+      { fetch: secondFetch },
+    );
+
+    expect(firstFetch).toHaveBeenCalledTimes(1);
+    expect(secondFetch).toHaveBeenCalledTimes(1);
+    expect(second).toMatchObject({
+      state: "ready",
+      item: {
+        id: "system-status",
+        severity: "danger",
+        value: "1 service down",
+      },
+    });
+  });
 });
 
 const testDocument = testDashboard();

apps/web/src/lib/server/datasources/index.ts

@@ -41,6 +41,7 @@ export type DashboardTileResolution =
 
 export interface DatasourceResolutionOptions {
   fetch?: DatasourceFetch;
+  now?: () => number;
   prometheusBaseUrl?: string;
   prometheusRangeSeconds?: number;
   prometheusStepSeconds?: number;
@@ -113,9 +114,7 @@ export async function resolveDashboardTile(
     const item = module.id === "runtime-health-summary"
       ? runtimeHealthSummary(
           module,
-          await Promise.all(
-            document.serviceGroups.map((group) => resolveServiceGroup(group, context)),
-          ),
+          await serviceGroupsSnapshot(document, context),
         )
       : await resolveModule(module, context);
 
@@ -132,7 +131,7 @@ export async function resolveDashboardTile(
     item: await resolveStatusTile(
       statusItem,
       document.metadata.refreshIntervalSeconds,
-      document.serviceGroups,
+      document,
       context,
     ),
   };
@@ -140,14 +139,27 @@ export async function resolveDashboardTile(
 
 interface DatasourceContext {
   fetch: DatasourceFetch;
+  fetchIdentity: number;
+  now: () => number;
   prometheusBaseUrl: string;
   prometheusRangeSeconds: number;
   prometheusStepSeconds: number;
   requestTimeoutMs: number;
+  serviceGroupsSnapshot?: Promise<ServiceGroup[]>;
 }
 
 type DatasourceFetch = (input: string, init?: RequestInit) => Promise<Response>;
 
+interface ServiceGroupsSnapshotEntry {
+  expiresAt: number;
+  snapshot: Promise<ServiceGroup[]>;
+}
+
+const serviceGroupsSnapshotTtlMs = 30_000;
+const serviceGroupsSnapshotCache = new Map<string, ServiceGroupsSnapshotEntry>();
+const datasourceFetchIdentities = new WeakMap<DatasourceFetch, number>();
+let nextDatasourceFetchIdentity = 1;
+
 interface PrometheusVectorResult {
   metric?: Record<string, string>;
   value?: [number, string];
@@ -159,8 +171,12 @@ interface PrometheusMatrixResult {
 }
 
 function datasourceContext(options: DatasourceResolutionOptions): DatasourceContext {
+  const fetch = options.fetch || globalThis.fetch;
+
   return {
-    fetch: options.fetch || globalThis.fetch,
+    fetch,
+    fetchIdentity: datasourceFetchIdentity(fetch),
+    now: options.now || Date.now,
     prometheusBaseUrl:
       options.prometheusBaseUrl ||
       process.env.PROMETHEUS_BASE_URL ||
@@ -171,6 +187,68 @@ function datasourceContext(options: DatasourceResolutionOptions): DatasourceCont
   };
 }
 
+function datasourceFetchIdentity(fetch: DatasourceFetch): number {
+  const existing = datasourceFetchIdentities.get(fetch);
+  if (existing) return existing;
+
+  const next = nextDatasourceFetchIdentity;
+  nextDatasourceFetchIdentity += 1;
+  datasourceFetchIdentities.set(fetch, next);
+  return next;
+}
+
+function serviceGroupsSnapshot(
+  document: DashboardDocument,
+  context: DatasourceContext,
+): Promise<ServiceGroup[]> {
+  if (context.serviceGroupsSnapshot) return context.serviceGroupsSnapshot;
+
+  const key = serviceGroupsSnapshotKey(document, context);
+  const now = context.now();
+  const cached = serviceGroupsSnapshotCache.get(key);
+  if (cached && cached.expiresAt > now) {
+    context.serviceGroupsSnapshot = cached.snapshot;
+    return cached.snapshot;
+  }
+
+  const snapshot = Promise.all(
+    document.serviceGroups.map((group) => resolveServiceGroup(group, context)),
+  );
+  context.serviceGroupsSnapshot = snapshot;
+  serviceGroupsSnapshotCache.set(key, {
+    expiresAt: now + serviceGroupsSnapshotTtlMs,
+    snapshot,
+  });
+  snapshot.catch(() => {
+    if (serviceGroupsSnapshotCache.get(key)?.snapshot === snapshot) {
+      serviceGroupsSnapshotCache.delete(key);
+    }
+  });
+  return snapshot;
+}
+
+function serviceGroupsSnapshotKey(
+  document: DashboardDocument,
+  context: DatasourceContext,
+): string {
+  return JSON.stringify(
+    {
+      fetchIdentity: context.fetchIdentity,
+      prometheusBaseUrl: context.prometheusBaseUrl,
+      prometheusRangeSeconds: context.prometheusRangeSeconds,
+      prometheusStepSeconds: context.prometheusStepSeconds,
+      requestTimeoutMs: context.requestTimeoutMs,
+      serviceGroups: document.serviceGroups.map((group) => ({
+        id: group.id,
+        services: group.services.map((service) => ({
+          datasource: service.datasource,
+          id: service.id,
+        })),
+      })),
+    },
+  );
+}
+
 async function resolveTelemetryCard(
   card: TelemetryCard,
   context: DatasourceContext,
@@ -485,13 +563,11 @@ function resolveStatusItem(
 async function resolveStatusTile(
   item: StatusItem,
   refreshIntervalSeconds: number | undefined,
-  serviceGroups: ServiceGroup[],
+  document: DashboardDocument,
   context: DatasourceContext,
 ): Promise<StatusItem> {
   if (item.id === "system-status") {
-    const resolvedGroups = await Promise.all(
-      serviceGroups.map((group) => resolveServiceGroup(group, context)),
-    );
+    const resolvedGroups = await serviceGroupsSnapshot(document, context);
     const health = serviceHealthSummary(resolvedGroups);
     return {
       ...structuredClone(item),